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    <meta charset="UTF-8">
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    <title>Document</title>
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<body>
    <script>
        var score = prompt("请输入您的成绩")
        if (score >= 90) {
            alert("A")
        } else if (score >= 80 && score < 90) {
            alert("B")
        } else if (score >= 70 && score < 80) {
            alert("C")
        } else if (score >= 60 && score < 70) {
            alert("D")
        } else {
            alert("E")
        }
    </script>
</body>

</html>